The present invention relates generally to the backup of information stored in a storage system, and, more particularly, to server-free backup of information on a storage area network (SAN).
As computer systems have treated an increasing amount of information in recent years, there is an increasing need for backing up such information. Thus, there is a tendency for the load imposed on backup processing of a server to be increased. Where a server backs up a large amount of data, the data is read from a storage system with which a source storage device to be backed up is connected, and then the data is written into a target backup device, such as a tape library, for example.
However, as the amount of data increases, the server resources (e.g., host bus adapter) used for the backup are occupied for a longer time. Thus, if another application program tries to use this host bus adapter to send and receive other data during this interval, the processing has to wait for a long time or the performance deteriorates greatly.
One means for alleviating the burden imposed on a server's backup processing to solve the above-described problems involves the backup of data using an Extended Copy command.
On the other hand, in an application where there is a large amount of I/O processing to and from a storage volume, in a case where the server issues a splitting instruction to pair volumes, an update copy from the source volume to the target volume may not be immediately ended. Rather, some time is taken until a split state is reached. To solve this problem, there is a technique that is available. In particular, when a server issues a splitting instruction to pair volumes, a storage controller continues an update copy to the target volume, while responding to the server that the pair volumes are in a split state.
Patent Reference 1: JP-A-2001-222355
Patent Reference 2: JP-A-2002-366310
However, where data is transferred to a backup device that is different from the server, it is only assured that the data in the storage device will be transferred to the server. Therefore, the consistency between the data transferred from the target volume to the backup device and the data in the source volume is not assured.
Furthermore, if a backup is performed after waiting until data to be updated is completely reflected in the target volume from the source volume, the server waits without being capable of giving an instruction for start of backup processing until the data to be updated is completely reflected in the target volume. The server needs to monitor the split state.